Many enamel frit compositions that can be used for the enamelling of objects of aluminum are known from the literature (e.g. U.S. Pat. No. 2,467,114, DE 2 244 067, DE 2 119 777, U.S. Pat. No. 2,925,351, CA 85: 36671p, CA 95: 174228g). Highly opaque, self-opacifying and chemically resistant enamelling cannot, however, be produced with these known enamel frits. For this reason, use has hitherto been made of the additional admixture of titanium dioxide, for example, as opacifier to the so-called mill batch in order so to obtain opaque, chemically resistant enamelling on aluminum. This mill addition (up to 20 wt.%) in the form of, for example, titanium dioxide leads to the titanium dioxide dispersing finely in the enamelling and, as a result of the high scattering power of the titanium dioxide, to the enamel layer masking the metal base.
In contrast to enamel frits for the enamelling of aluminum, self-opacifying enamel frits based on titanium dioxide for steel have already existed for a relatively long time, but they cannot be applied to aluminum, since they crystallize at temperatures of 590.degree. C. to 650.degree. C.